JP6697361B2 - Hydraulic excavator drive system - Google Patents

Description

  The present invention relates to a hydraulic excavator drive system.

  Generally, in a hydraulic excavator, an arm is swingably connected to a tip end of a boom that leans against a revolving structure, and a bucket is swingably connected to a tip end of the arm. The drive system mounted on this hydraulic excavator includes a boom cylinder that raises the boom, an arm cylinder that swings the arm, a bucket cylinder that swings the bucket, and the like. Hydraulic oil is supplied.

  For example, Patent Document 1 discloses a hydraulic excavator drive system 100 as shown in FIG. In this drive system 100, the supply and discharge of hydraulic oil to and from the arm cylinder 110 are controlled by the control valve 150. The control valve 150 has a pair of pilot ports connected to the pilot operation valve 140, and as the pilot pressure introduced to the control valve 150 increases, the opening area on the meter-in side and the opening on the meter-out side of the control valve 150 are increased. The area becomes large.

  Further, in the drive system 100, the pilot opening / closing valve 120 is provided in the supply / discharge line that connects the rod-side oil chamber 112 of the arm cylinder 110 and the control valve 150. The pilot opening / closing valve 120 operates when the pressure in the bottom side oil chamber 111 of the arm cylinder 110 drops below a predetermined pressure, and serves as a passage for the working oil discharged from the rod side oil chamber 112 of the arm cylinder 110. Openness is reduced. This prevents the arm cylinder 110 from extending due to the weight of the entire arm and bucket during the arm pulling operation, and prevents cavitation from occurring in the arm cylinder 110.

JP-A-5-187409

  However, in the drive system 100 shown in FIG. 8, in addition to the pilot opening / closing valve 120, the pilot pressure introduced from the pilot operating valve 140 to the pilot opening / closing valve 120 is used as a valve for operating the pilot opening / closing valve 120. The pressure reducing valve 130 for reducing the pressure according to the pressure in the bottom side oil chamber 111 is required. Therefore, the configuration of the drive system 100 is complicated and the cost is high.

  Therefore, an object of the present invention is to provide a hydraulic excavator drive system capable of preventing cavitation from occurring in a cylinder that swings an arm or a bucket due to the influence of gravity with an inexpensive configuration.

  In order to solve the above problems, a hydraulic excavator drive system according to one aspect of the present invention is a cylinder that rocks a rocking part that is an arm or a bucket, and a control that controls supply and discharge of hydraulic oil to and from the cylinder. A control valve having a first pilot port for a first operation for bringing the swinging part closer to the cabin and a second pilot port for a second operation for moving the swinging part away from the cabin; and an operating lever. An operation device that outputs an operation signal according to the tilt angle of the operation lever when receiving either the first operation or the second operation; and a solenoid proportional valve connected to the first pilot port. A control device that controls the electromagnetic proportional valve based on the operation signal, wherein the control device is configured to control the electromagnetic ratio when the operation device receives the first operation. The pilot pressure output from the valve is proportional to the operation signal output from the operating device up to the upper limit pressure, and when the swinging part is an arm, the center of gravity of the arm and the bucket is the swinging part. Is a bucket, as long as the center of gravity of the bucket is located on the opposite side of the cabin with respect to the vertical line passing through at least the swing center of the swing section, the upper limit is the closer the swing section is to the cabin. The solenoid proportional valve is controlled so that the pressure rises.

  According to the above configuration, at the time of the first operation, the center of gravity of the gravity-affected zone, which is the entire arm and the bucket or the bucket (hereinafter, may be abbreviated as the gravity center of the gravity-affected zone), is farthest from the cabin. In other words, in other words, when gravity acts on the oscillating portion so as to most accelerate the oscillating movement of the oscillating portion, the upper limit pressure of the pilot pressure output from the solenoid proportional valve becomes the minimum. That is, the maximum opening area on the meter-out side of the control valve when the operating lever of the operating device is largely tilted can be made smaller as the center of gravity of the gravity-affected portion is farther from the cabin. Therefore, when the rocking portion rocks according to gravity, it is possible to prevent cavitation from occurring in the cylinder due to the influence of gravity. Moreover, it can be realized with an inexpensive structure using one solenoid proportional valve for the first operation.

  When the operating device receives the first operation, the control device sets the upper limit pressure to increase as the swinging part is closer to the cabin in the entire swinging range of the swinging part. The solenoid proportional valve may be controlled. According to this configuration, when the center of gravity of the gravity-affected portion is closest to the cabin during the first operation, in other words, when gravity acts on the swing portion to slow down the swing of the swing portion most, The upper limit pressure of the pilot pressure output from the solenoid proportional valve becomes maximum. That is, the maximum opening area on the meter-out side of the control valve when the operating lever of the operating device is largely tilted can be increased as the gravity center of the gravity-affected portion is closer to the cabin. Therefore, when the swinging part swings against gravity, the maximum opening area on the meter-out side of the control valve when the operating lever of the operating device is tilted greatly increases, so that the hydraulic oil discharged from the cylinder is Throttling by the control valve is suppressed. Therefore, when the center of gravity of the gravity-affected portion is located on the same side as the cabin with respect to the vertical line, the power required for swinging the swinging portion can be reduced.

  The solenoid proportional valve is a first solenoid proportional valve, and further includes a second solenoid proportional valve connected to the second pilot port, wherein the control device is configured such that when the operating device receives the second operation, The pilot pressure output from the second solenoid proportional valve is proportional to the operation signal output from the operating device up to the upper limit pressure, and when the swinging portion is an arm, the center of gravity of the arm and the bucket as a whole is When the swing portion is a bucket, the swing portion is the cabin as long as the center of gravity of the bucket is located on the same side as the cabin with respect to a vertical line passing through at least the swing center of the swing portion. The second solenoid proportional valve may be controlled such that the upper limit pressure increases as the distance from the second solenoid valve increases. According to this configuration, when the center of gravity of the gravity-affected portion is closest to the cabin during the second operation, in other words, when gravity acts on the swing portion so as to accelerate the swing of the swing portion the most. , The upper limit pressure of the pilot pressure output from the second solenoid proportional valve becomes minimum. That is, the maximum opening area on the meter-out side of the control valve when the operating lever of the operating device is largely tilted can be made smaller as the center of gravity of the gravity-affected portion is closer to the cabin. Therefore, when the rocking portion rocks according to gravity, it is possible to prevent cavitation from occurring in the cylinder due to the influence of gravity. Moreover, it can be realized with an inexpensive configuration using one solenoid proportional valve for the second operation.

  When the operating device receives the second operation, the control device sets the upper limit pressure to increase as the swinging part is farther from the cabin, in the entire swinging range of the swinging part. The second proportional solenoid valve may be controlled. According to this configuration, when the center of gravity of the gravity-affected portion is farthest from the cabin during the second operation, in other words, when gravity acts on the swing portion so as to slow down the swing of the swing portion most. The upper limit pressure of the pilot pressure output from the second solenoid proportional valve becomes maximum. That is, the maximum opening area on the meter-out side of the control valve when the operating lever of the operating device is largely tilted can be increased as the center of gravity of the gravity-affected portion is farther from the cabin. Therefore, when the swinging part swings against gravity, the maximum opening area on the meter-out side of the control valve when the operating lever of the operating device is tilted greatly increases, so that the hydraulic oil discharged from the cylinder is Throttling by the control valve is suppressed. Therefore, when the center of gravity of the gravity-affected portion is located on the opposite side of the cabin with respect to the vertical line, the power required for swinging the swinging portion can be reduced.

  A hydraulic excavator drive system according to another aspect of the present invention is a cylinder that rocks a rocking part that is an arm or a bucket, and a control valve that controls supply and discharge of hydraulic oil to and from the cylinder. The first operation includes a control valve having a first pilot port for a first operation for bringing the swinging part closer to the cabin and a second pilot port for a second operation for moving the swinging part away from the cabin, and an operating lever. And an operation device that outputs an operation signal according to the tilt angle of the operation lever when receiving one of the second operations, an electromagnetic proportional valve connected to the second pilot port, and an operation signal based on the operation signal. And a control device for controlling the electromagnetic proportional valve, wherein the control device outputs a pie output from the electromagnetic proportional valve when the operating device receives the second operation. Up to the upper limit pressure, and when the swinging portion is an arm, the center of gravity of the arm and the bucket as a whole is the bucket pressure, and the swinging portion is the bucket. As long as the center of gravity of the bucket is located on the same side as the cabin with respect to a vertical line passing through at least the swing center of the swing unit, the upper limit pressure becomes higher as the swing unit is farther from the cabin. The solenoid proportional valve is controlled so as to rise.

  According to the above configuration, when the center of gravity of the gravity-affected portion is closest to the cabin during the second operation, in other words, when gravity acts on the swing portion to accelerate the swing of the swing portion most. In addition, the upper limit pressure of the pilot pressure output from the solenoid proportional valve becomes minimum. That is, the maximum opening area on the meter-out side of the control valve when the operating lever of the operating device is largely tilted can be made smaller as the center of gravity of the gravity-affected portion is closer to the cabin. Therefore, when the rocking portion rocks according to gravity, it is possible to prevent cavitation from occurring in the cylinder due to the influence of gravity. Moreover, it can be realized with an inexpensive configuration using one solenoid proportional valve for the second operation.

  When the operating device receives the second operation, the control device sets the upper limit pressure to increase as the swinging part is farther from the cabin, in the entire swinging range of the swinging part. The solenoid proportional valve may be controlled. According to this configuration, when the center of gravity of the gravity-affected portion is farthest from the cabin during the second operation, in other words, when gravity acts on the swing portion so as to slow down the swing of the swing portion most. The upper limit pressure of the pilot pressure output from the solenoid proportional valve becomes maximum. That is, the maximum opening area on the meter-out side of the control valve when the operating lever of the operating device is largely tilted can be increased as the center of gravity of the gravity-affected portion is farther from the cabin. Therefore, when the swinging part swings against gravity, the maximum opening area on the meter-out side of the control valve when the operating lever of the operating device is tilted greatly increases, so that the hydraulic oil discharged from the cylinder is Throttling by the control valve is suppressed. Therefore, when the center of gravity of the gravity-affected portion is located on the opposite side of the cabin with respect to the vertical line, the power required for swinging the swinging portion can be reduced.

  The hydraulic excavator drive system further includes a revolving structure and a camera attached to the revolving structure for photographing the swinging unit, and the control device determines the center of gravity from the image photographed by the camera. The upper limit pressure may be determined in accordance with the swing angle between the vertical line and the line connecting the swing center of the swing portion and the swing center. It is possible to provide a stroke sensor on the boom cylinder and the arm cylinder, or on the boom cylinder, the arm cylinder and the bucket cylinder, and calculate the swing angle of the swing portion from the detection values of these stroke sensors. However, since large vibrations act on those cylinders, it is necessary to take measures against vibrations when the stroke sensor is used. Further, for example, when the swing unit is an arm, both the stroke detection value of the boom cylinder and the stroke detection value of the arm cylinder are required to calculate the swing angle of the arm. On the other hand, if a camera is attached to a swinging body with little vibration and the rocking angle of the rocking portion is obtained from the image captured by the camera, the adverse effect of vibration can be avoided with a simple configuration.

  The hydraulic excavator drive system further includes a traveling body that supports the revolving structure so that the revolving structure is capable of revolving, and an inclination sensor that is attached to the revolving structure and that detects the levelness of the revolving structure. A virtual straight line parallel to the turning axis of the revolving structure, wherein the control device corrects the swing angle obtained from the image captured by the camera based on the horizontality detected by the tilt sensor. May be. According to this configuration, the swing angle of the swing portion can be accurately obtained regardless of the inclination of the ground.

  According to the present invention, it is possible to prevent cavitation from occurring in a cylinder that swings an arm or a bucket due to the influence of gravity with an inexpensive configuration.

It is a schematic structure figure of a hydraulic excavator drive system concerning a 1st embodiment of the present invention. It is a side view of a hydraulic excavator. It is a graph which shows the relationship between the pilot pressure to a control valve, and the opening area of a control valve. 6 is a graph showing the relationship between the tilt angle of the operating lever and the pilot pressure output from the solenoid proportional valve. 7 is a graph showing the relationship between the swing angle of the arm and the upper limit pressure of the pilot pressure output from the solenoid proportional valve. 6 is a graph showing a change over time in the opening area of the control valve on the meter-out side when the operation lever is largely tilted and swung from the position farthest from the cabin to the position closest to the cabin. It is a schematic block diagram of the hydraulic excavator drive system which concerns on 2nd Embodiment of this invention. It is a schematic block diagram of the conventional hydraulic excavator drive system.

(First embodiment)
FIG. 1 shows a hydraulic excavator drive system 1A according to a first embodiment of the present invention, and FIG. 2 shows a hydraulic excavator 10 equipped with the drive system 1A.

  The hydraulic excavator 10 shown in FIG. 2 is a self-propelled type and includes a traveling body 11. The hydraulic excavator 10 also includes a revolving structure 12 that is supported by the traveling structure 11 so as to be revolvable, and a boom 13 that leans against the revolving structure 12. An arm 14 is swingably connected to the tip of the boom 13, and a bucket 15 is swingably connected to the tip of the arm 14. The revolving structure 12 is provided with a cabin 16 in which a driver's seat is installed.

  As shown in FIG. 1, the drive system 1A includes, as hydraulic actuators, a pair of left and right traveling motors and a swing motor (not shown), and a boom cylinder 21 (see FIG. 2), an arm cylinder 22 and a bucket cylinder 23. The boom cylinder 21 raises the boom 13, the arm cylinder 22 swings the arm 14, and the bucket cylinder 23 swings the bucket 15.

  Hydraulic oil is supplied to the above-described hydraulic actuator from the main pump 31 via a control valve. The main pump 31 is driven by the engine 30. For example, the working oil is supplied to the arm cylinder 22 via the arm control valve 41, and the working oil is supplied to the bucket cylinder 23 via the bucket control valve 44. Illustration of other control valves for hydraulic actuators is omitted. The main pump 31 may be a single pump or a double pump.

  Specifically, the arm control valve 41 and the bucket control valve 44 are connected to the main pump 31 by the supply line 32. Further, each of the arm control valve 41 and the bucket control valve 44 is connected to the tank by the tank line 35.

  The arm control valve 41 is connected to the arm cylinder 22 by a pair of supply / discharge lines 22a and 22b. The arm control valve 41 controls supply and discharge of hydraulic oil to and from the arm cylinder 22. The arm control valve 41 has a first pilot port 43 for an arm pulling operation that brings the arm 14 closer to the cabin 16, and a second pilot port 42 for an arm pushing operation that moves the arm 14 away from the cabin 16.

  Similarly, the bucket control valve 44 is connected to the bucket cylinder 23 by a pair of supply / discharge lines 23a and 23b. The bucket control valve 44 controls supply and discharge of hydraulic oil to and from the bucket cylinder 23. The bucket control valve 44 has a first pilot port 46 for bucket-in operation that brings the bucket 15 closer to the cabin 16, and a second pilot port 45 for bucket-out operation that keeps the bucket 15 away from the cabin 16.

  Further, the drive system 1A includes an arm operating device 61 for moving the arm control valve 41 and a bucket operating device 62 for moving the bucket control valve 44. The arm operation device 61 includes an operation lever, and outputs an operation signal according to the tilt angle of the operation lever when either the arm pulling operation or the arm pushing operation is received. The bucket operation device 62 includes an operation lever and outputs an operation signal according to the tilt angle of the operation lever when receiving either a bucket-in operation or a bucket-out operation.

  In the present embodiment, the arm operating device 61 and the bucket operating device 62 are pilot operated valves that output pilot pressure as an operation signal. The pilot pressure output when the arm operating device 61 receives the arm pulling operation (when the operating lever is tilted in the arm pulling direction) is detected by the first pressure gauge 81, and the arm operating device 61 receives the arm pushing operation. When the operating lever is tilted in the arm pushing direction, the pilot pressure output is detected by the second pressure gauge 82. Similarly, the pilot pressure output when the bucket operating device 62 receives the bucket in operation (when the operating lever is tilted in the bucket in direction) is detected by the third pressure gauge 83, and the bucket operating device 62 outputs the bucket out. The pilot pressure output when an operation is received (when the operation lever is tilted in the bucket out direction) is detected by the fourth pressure gauge 84. The pilot pressures detected by the first to fourth pressure gauges 81 to 84 are input to the control device 7.

  The second pilot port 42 of the arm control valve 41 described above is connected to the arm operating device 61 by the arm pushing pilot line 63. On the other hand, the first pilot port 43 is connected to the arm electromagnetic proportional valve 51 by an arm pulling pilot line 64.

  Similarly, the second pilot port 45 of the bucket control valve 44 is connected to the bucket operating device 62 by the bucket-out pilot line 65. On the other hand, the first pilot port 46 is connected to the bucket solenoid proportional valve 52 by a bucket-in pilot line 66.

  The arm proportional solenoid valve 51 and the bucket proportional solenoid valve 52 are connected to the sub pump 33 by a primary pressure line 34. The sub pump 33 is driven by the engine 30, like the main pump 31.

  The control device 7 described above has, for example, a memory such as a ROM or RAM and a CPU. The control device 7 controls the electromagnetic proportional valve 51 for arm based on an operation signal (pilot pressure detected by the first pressure gauge 81 in this embodiment) output from the arm operation device 61 during the arm pulling operation, During the bucket-in operation, the bucket solenoid proportional valve 52 is controlled based on an operation signal output from the bucket operation device 62 (in the present embodiment, the pilot pressure detected by the third pressure gauge 83).

  In the present embodiment, each solenoid proportional valve 51, 52 is a direct proportional type in which the output pilot pressure (secondary pressure) has a positive correlation with the command current. However, each solenoid proportional valve 51, 52 may be an inverse proportional type in which the output pilot pressure has a negative correlation with the command current.

  Specifically, the control device 7 sends a command current to the arm electromagnetic proportional valve 51 during the arm pulling operation, and sends a command current to the bucket electromagnetic proportional valve 52 during the bucket in operation. During the arm pushing operation, the pilot pressure output from the arm operating device 61 is guided to the second pilot port 42 of the arm control valve 41, so that the arm control valve 41 has a tilt angle of the operating lever of the arm operating device 61. Controlled accordingly. Similarly, during the arm-out operation, the pilot pressure output from the bucket operating device 62 is guided to the second pilot port 45 of the bucket control valve 44, so that the bucket control valve 44 causes the tilting angle of the operating lever of the bucket operating device 62 to increase. Controlled according to.

  During the bucket-in operation, the control device 7 controls the bucket electromagnetic proportional valve 52 so that the pilot pressure output from the bucket electromagnetic proportional valve 52 is proportional to the operation signal output from the bucket operating device 62. That is, the control device 7 sends a command current proportional to the operation signal output from the bucket operation device 62 to the bucket solenoid proportional valve 52.

  In the present embodiment, control based on the upper limit pressure PL described below is performed during the arm pulling operation. That is, in the present embodiment, the arm 14 corresponds to the swinging portion of the present invention, and the arm pulling operation and the arm pushing operation correspond to the first operation and the second operation of the present invention, respectively.

  During the arm pulling operation, the control device 7 controls the pilot pressure output from the arm electromagnetic proportional valve 51 to be proportional to the operation signal output from the arm operating device 61 up to the upper limit pressure PL, as shown in FIG. First, the solenoid proportional valve 51 for arm is controlled. That is, the control device 7 supplies a command current proportional to the operation signal output from the arm operating device 61 until the pilot pressure output from the arm electromagnetic proportional valve 51 reaches the upper limit pressure PL. Even if the operating lever of the arm operating device 61 is tilted further, the command current to be sent to the arm electromagnetic proportional valve 51 is maintained at a value corresponding to the upper limit pressure PL.

  Further, the controller 7 controls the arm proportional solenoid valve 51 so that the upper limit pressure PL increases as the arm 14 is closer to the cabin 16. In the present embodiment, such control is performed in the entire swing range of the arm 14.

  As shown in FIG. 2, in the present embodiment, a camera 71 for photographing the arm 14 is attached to the cabin 16 of the swing body 12. Then, the control device 7 obtains the swing angle θ of the arm 14 from the image taken by the camera 71. The swing angle θ of the arm 14 is an angle between a line connecting the center of gravity of the gravity-affected part, which is the entire arm 14 and the bucket 15, and the swing center 14a of the arm 14 and a vertical line L passing through the swing center 14a. is there. The center of gravity may be a predetermined point or a point that changes according to the attitude of the bucket 15.

  Specifically, the control device 7 calculates the swing angle θ of the arm 14 by comparing the image captured by the camera 71 with reference data stored in advance. In this case, the vertical line L passing through the swing center 14a of the arm 14 is an imaginary straight line parallel to the swing axis of the swing body 12 regardless of the levelness of the swing body 12. After obtaining the swing angle θ of the arm 14, the control device 7 determines the upper limit pressure PL according to the swing angle θ.

  The swing angle θ of the arm 14 becomes zero when the center of gravity of the gravity-affected portion is on the vertical line L, and when the arm is pulled, the side far from the cabin 16 is positive and the side close to the cabin 16 is negative.

  In the present embodiment, as shown in FIG. 5, the arm 14 swings from the position farthest from the cabin 16 to the position closest to the cabin 16, in other words, the swing angle θ of the arm 14 is the maximum angle θmax ( When it decreases from the positive value) to the minimum angle θmin (negative value), the upper limit pressure PL increases from P1 to P2. Therefore, as shown in FIG. 4, the maximum pilot pressure when the operation lever of the arm operation device 61 is fully tilted changes between P1 and P2 according to the swing angle θ of the arm 14. Therefore, as shown in FIG. 3, the maximum opening area of the arm control valve 41 on the meter-out side when the operating lever of the arm operating device 61 is largely tilted is when the swing angle θ of the arm 14 is the maximum angle θmax. Becomes smaller than A1 and becomes larger than A2 when the swing angle θ of the arm 14 is the minimum angle θmin.

  For example, when the operating lever of the arm operating device 61 is fully tilted until the swinging angle θ of the arm 14 reaches the minimum angle θmin in the state where the swinging angle θ of the arm 14 is the maximum angle θmax, it is shown in FIG. As described above, the opening area of the arm control valve 41 on the meter-out side first rapidly increases to A1 and then gradually increases to A2 in accordance with the change in the swing angle θ.

  Further, in the present embodiment, as shown in FIG. 2, the tilt sensor 72 is attached to the revolving unit 12. Although the inclination sensor 72 is arranged in the cabin 16 in the illustrated example, the inclination sensor 72 may be arranged in another portion (for example, the engine room). The tilt sensor 72 detects the levelness of the swing body 12. Then, the control device 7 corrects the swing angle θ of the arm 14 obtained from the image captured by the camera 71, based on the horizontality detected by the tilt sensor 72. For example, in the case where the revolving unit 12 is moving forward and downward, the swing angle θ of the arm 14 obtained from the image captured by the camera 71 is used to detect the tilt angle of the revolving unit 12 from the swing angle θ (detected by the tilt sensor 72). Correct the horizontal level).

  As described above, in the drive system 1A of the present embodiment, when the gravity center of the gravity-affected portion (the arm 14 and the entire bucket 15) is farthest from the cabin 16 during the arm pulling operation, in other words, gravity is applied to the arm 14. When acting to accelerate the swing of the arm 14 most, the upper limit pressure PL of the pilot pressure output from the arm proportional solenoid valve 51 becomes the minimum P1. That is, the maximum opening area on the meter-out side of the arm control valve 41 when the operation lever of the arm operation device 61 is largely tilted is such that the farther the center of gravity of the gravity-affected portion is from the cabin 16 (that is, the swinging of the arm 14). The larger the dynamic angle θ, the smaller the angle. Therefore, when the arm 14 swings according to gravity, it is possible to prevent cavitation from occurring in the arm cylinder 22 due to the influence of gravity. Moreover, this can be realized with an inexpensive structure using one arm solenoid proportional valve 51 for the arm pulling operation.

  On the other hand, when the center of gravity of the gravity-affected portion is closest to the cabin 16 during the arm pulling operation, in other words, when gravity acts on the arm 14 so as to most decelerate the swing of the arm 14, the electromagnetic proportional force for the arm is increased. The upper limit pressure PL of the pilot pressure output from the valve 51 becomes maximum P2. That is, the maximum opening area on the meter-out side of the arm control valve 41 when the operating lever of the arm operating device 61 is largely tilted is such that the gravity center of the gravity-affected portion is closer to the cabin 16 (that is, the swing angle of the arm 14). It can be increased (the smaller θ is). Therefore, when the arm 14 swings against gravity, the maximum opening area on the meter-out side of the arm control valve 41 becomes large when the operation lever of the arm operation device 61 is largely tilted, so that the arm cylinder 22 is discharged from the arm cylinder 22. It is possible to prevent the hydraulic oil to be throttled by the arm control valve 41. Therefore, when the center of gravity of the gravity-affected portion is located on the same side as the cabin 16 with respect to the vertical line L, the power required to swing the arm 14 can be reduced.

  Here, a case where the control based on the upper limit pressure PL is not performed will be described. In this case, as shown by the chain double-dashed line in FIG. 3, the opening area on the meter-out side of the arm control valve 41 must be smaller than the opening area on the meter-out side (solid line) in this embodiment. This is because the maximum opening area on the meter-out side of the arm control valve 41 when the control based on the upper limit pressure PL is not performed is the worst condition (the swing angle θ of the arm 14 is the maximum angle θmax and the arm operating device is This is because it is set so that cavitation does not occur in the arm cylinder 22 when the operation lever 61 is fully tilted. Therefore, the operating oil discharged from the arm cylinder 22 is unnecessarily throttled by the arm control valve 41 except under the worst condition.

  On the other hand, in the present embodiment, the maximum opening area on the meter-out side of the arm control valve 41 when the operation lever of the arm operation device 61 is largely tilted changes according to the swing angle θ of the arm 14. Therefore, the opening area on the meter-out side of the arm control valve 41 can be made significantly larger than the opening area on the meter-out side of the arm control valve 41 when the control based on the upper limit pressure PL is not performed.

  By the way, it is possible to provide a stroke sensor in the boom cylinder 21 and the arm cylinder 22, and calculate the swing angle θ of the arm 14 from the detection values of these stroke sensors. However, since a large vibration acts on the boom cylinder 21 and the arm cylinder 22, it is necessary to take measures against vibration when the stroke sensor is used. Further, both the stroke detection value of the boom cylinder 21 and the stroke detection value of the arm cylinder 22 are required to calculate the swing angle θ of the arm 14. On the other hand, if the camera 71 is attached to the revolving unit 12 with less vibration as in the present embodiment and the swing angle θ of the arm 14 is obtained from the image captured by the camera 71, the adverse effect of vibration can be obtained with a simple configuration. Can be avoided.

  Furthermore, in the present embodiment, the swing angle θ of the arm 14 obtained from the image captured by the camera 71 is corrected based on the horizontality of the revolving unit 12 detected by the tilt sensor 72, so The swing angle θ can be accurately obtained regardless of the inclination of the ground.

<Modification>
The bucket solenoid proportional valve 52 may be omitted, and the bucket operating device 62, which is a pilot operating valve, may be connected to the first pilot port 46 of the bucket control valve 44 by the bucket in pilot line 66. However, if the bucket solenoid proportional valve 52 is provided, the control based on the upper limit pressure PL can be performed even during the bucket-in operation. Alternatively, the control based on the upper limit pressure PL may be performed only during the bucket-in operation without performing during the arm pulling operation. In this case, the arm proportional solenoid valve 51 may be omitted, and the arm operating device 61, which is a pilot operating valve, may be connected to the first pilot port 43 of the arm control valve 41 by the arm pulling pilot line 64.

  When the control based on the upper limit pressure PL is performed during the bucket in operation, the bucket 15 corresponds to the swinging portion of the present invention, and the bucket in operation and the bucket out operation correspond to the first operation and the second operation of the present invention, respectively. In this case, similarly to the above-described embodiment, the control device 7 controls the bucket proportional solenoid valve 52 so that the pilot pressure output from the bucket proportional proportional valve 52 is proportional to the operation signal output from the bucket operating device 62 up to the upper limit pressure PL. The bucket solenoid proportional valve 52 is controlled. That is, until the pilot pressure output from the bucket electromagnetic proportional valve 52 reaches the upper limit pressure PL, the control device 7 supplies a command current proportional to the operation signal output from the bucket operating device 62 to the bucket electromagnetic proportional valve 52. Even if the operating lever of the bucket operating device 62 is tilted further, the command current to be sent to the bucket solenoid proportional valve 52 is maintained at a value corresponding to the upper limit pressure PL.

  Further, the control device 7 controls the bucket proportional solenoid valve 52 so that the upper limit pressure PL increases as the bucket 15 is closer to the cabin 16 in the entire swing range of the bucket 15. In this case, the bucket 15 may be photographed by the camera 71 attached to the cabin 16. Then, the control device 7 determines, from the image captured by the camera 71, a vertical line passing through the swing center 15a and a line connecting the center of gravity of the bucket 15 (gravitational influence part) and the swing center 15a (see FIG. 2) of the bucket 15. The swing angle of the bucket 15 which is the angle between the line and the line is determined, and the upper limit pressure PL is determined according to this swing angle.

  With such a configuration, it is possible to obtain the same effect as that of the above-described embodiment (the arm 14 is replaced with the bucket 15 in the effect of the above-described embodiment).

  Further, in the above-described embodiment, the upper limit pressure PL increases as the arm 14 is closer to the cabin 16 in the entire swing range of the arm 14. However, as long as the center of gravity of the gravity-affected portion (the arm 14 and the entire bucket 15) is located on the opposite side of the cabin 16 with respect to at least the vertical line L, even if the arm 14 is closer to the cabin 16, the upper limit pressure PL increases. Good. This point is the same when the control based on the upper limit pressure PL is performed during the bucket-in operation.

(Second embodiment)
Next, with reference to FIG. 7, a hydraulic excavator drive system 1B according to a second embodiment of the present invention will be described.

  In the present embodiment, the arm operating device 61 and the bucket operating device 62 are electric joysticks that output an electric signal to the control device 7 as an operation signal. Therefore, the second pilot port 42 of the arm control valve 41 is connected to the arm electromagnetic proportional valve 53 by the arm pushing pilot line 63, and the second pilot port 45 of the bucket control valve 44 is connected to the bucket out pilot line 65. Is connected to the bucket solenoid proportional valve 54. Note that in FIG. 7, only some signal lines are drawn for simplification of the drawing.

  In the present embodiment, the control based on the upper limit pressure PL described in the first embodiment may be performed only during the arm pulling operation, or may be performed only during the bucket in operation. Alternatively, in the present embodiment, the control based on the upper limit pressure PL described in the first embodiment may be performed only during the arm pushing operation or may be performed only during the bucket out operation.

  Further, the control based on the upper limit pressure PL may be performed during the arm pulling operation and the arm pushing operation. In this case, the arm solenoid proportional valve 51 corresponds to the first solenoid proportional valve of the present invention, and the arm solenoid proportional valve 53 corresponds to the second solenoid proportional valve of the present invention. Alternatively, the control based on the upper limit pressure PL may be performed during the bucket in operation and the bucket out operation.

  For example, when the control based on the upper limit pressure PL is performed during the arm pushing operation, the control device 7 controls the operation signal output from the arm operating device 61 until the pilot pressure output from the arm electromagnetic proportional valve 53 is up to the upper limit pressure PL. The electromagnetic proportional valve for arm 53 is controlled so as to be proportional to. During the arm pushing operation, the control device 7 causes the arm 14 to move from the cabin 16 as long as the gravity center of the gravity-affected portion (the arm 14 and the entire bucket 15) is located on the same side as the cabin 16 with respect to at least the vertical line L. The arm proportional solenoid valve 53 may be controlled so that the upper limit pressure PL increases as the distance increases. The upper limit pressure PL is determined in the same manner as described in the first embodiment.

  The swing angle θ of the arm 14 becomes zero when the center of gravity of the gravity-affected portion is on the vertical line L, and when the arm is pushed, the side closer to the cabin 16 is plus and the side farther from the cabin 16 is minus.

  According to the above configuration, the maximum opening area on the meter-out side of the arm control valve 41 when the operation lever of the arm operation device 61 is largely tilted during the arm pushing operation is such that the center of gravity of the gravity-affected portion is close to the cabin 16. It can be made smaller (that is, as the swing angle θ of the arm 14 is larger). Therefore, when the arm 14 swings according to gravity, it is possible to prevent cavitation from occurring in the arm cylinder 22 due to the influence of gravity. Moreover, it can be realized with an inexpensive configuration using one arm solenoid proportional valve 53 for the arm pushing operation.

  Further, when the upper limit pressure PL increases as the arm 14 is farther from the cabin 16 in the entire swing range of the arm 14, the arm control valve 41 when the operation lever of the arm operation device 61 is largely tilted. The maximum opening area on the meter-out side can be increased as the center of gravity of the gravity-affected portion is farther from the cabin 16 (that is, the swing angle θ of the arm 14 is smaller). Therefore, when the arm 14 swings against gravity, the maximum opening area on the meter-out side of the arm control valve 41 when the operating lever of the arm operating device 61 is largely tilted becomes large, and therefore the discharge from the arm cylinder 22 is performed. It is possible to prevent the hydraulic oil to be throttled by the arm control valve 41. Therefore, when the center of gravity of the gravity-affected portion is located on the opposite side of the cabin 16 with respect to the vertical line L, the power required to swing the arm 14 can be reduced.

(Other embodiments)
The present invention is not limited to the above-described first and second embodiments, and various modifications can be made without departing from the gist of the present invention.

  For example, each of the arm control valve 41 and the bucket control valve 44 does not necessarily have to be a single control valve, and may be divided into a meter-in control valve and a meter-out control valve. An electric motor may be used instead of the engine 30.

  Furthermore, the hydraulic excavator 10 on which the drive system (1A or 1B) is mounted does not necessarily have to be self-propelled. For example, when the hydraulic excavator 10 is mounted on a ship, the revolving structure 12 may be rotatably supported by the hull.

1A, 1B Hydraulic excavator drive system 10 Hydraulic excavator 11 Traveling body 12 Revolving structure 14 Arm (oscillating part)
15 buckets (oscillating part)
22 Arm Cylinder 23 Bucket Cylinder 41 Arm Control Valve 42 Second Pilot Port 43 First Pilot Port 44 Bucket Control Valve 45 Second Pilot Port 46 First Pilot Port 51, 52, 53, 54 Electromagnetic Proportional Valve 61 Arm Operating Device 62 Bucket Operating device 7 Control device 71 Camera 72 Tilt sensor

Claims (8)

A cylinder for rocking the rocking part which is an arm or a bucket,
A control valve for controlling supply and discharge of hydraulic oil to and from the cylinder, the first pilot port for a first operation for bringing the swinging portion closer to the cabin and the second pilot for moving the swinging portion away from the cabin. A control valve having a second pilot port,
An operation device including an operation lever, which outputs an operation signal according to a tilt angle of the operation lever when receiving either the first operation or the second operation,
An electromagnetic proportional valve connected to the first pilot port,
A control device for controlling the solenoid proportional valve based on the operation signal,
The control device, when the operating device receives the first operation, a pilot pressure output from the solenoid proportional valve is proportional to an operation signal output from the operating device up to an upper limit pressure, and When the swinging part is an arm, the center of gravity of the arm and the entire bucket, and when the swinging part is a bucket, the center of gravity of the bucket is at least the vertical line passing through the swinging center of the swinging part. A hydraulic excavator drive system that controls the solenoid proportional valve so that the upper limit pressure increases as the swinging portion is closer to the cabin as long as it is located on the opposite side.   When the operating device receives the first operation, the control device sets the upper limit pressure to increase as the swinging part is closer to the cabin in the entire swinging range of the swinging part. The hydraulic excavator drive system according to claim 1, which controls an electromagnetic proportional valve. The solenoid proportional valve is a first solenoid proportional valve,
Further comprising a second solenoid proportional valve connected to the second pilot port,
The control device is such that, when the operating device receives the second operation, the pilot pressure output from the second electromagnetic proportional valve is proportional to an operating signal output from the operating device up to an upper limit pressure, and When the rocking portion is an arm, the center of gravity of the arm and the bucket as a whole, and when the rocking portion is a bucket, the center of gravity of the bucket is based on a vertical line passing at least the rocking center of the rocking portion. The second electromagnetic proportional valve is controlled so that the upper limit pressure increases as the swinging portion is farther from the cabin as long as it is located on the same side as the cabin. Hydraulic excavator drive system.   When the operating device receives the second operation, the control device sets the upper limit pressure to increase as the swinging part is farther from the cabin in the entire swinging range of the swinging part. The hydraulic excavator drive system according to claim 3, wherein the second solenoid proportional valve is controlled. A cylinder for rocking the rocking part, which is an arm or a bucket,
A control valve for controlling supply and discharge of hydraulic oil to and from the cylinder, comprising a first pilot port for a first operation for bringing the swinging portion closer to a cabin and a second operation port for moving the swinging portion away from the cabin. A control valve having a second pilot port,
An operation device including an operation lever, which outputs an operation signal according to a tilt angle of the operation lever when receiving either the first operation or the second operation,
An electromagnetic proportional valve connected to the second pilot port,
A control device for controlling the solenoid proportional valve based on the operation signal,
The control device, when the operating device receives the second operation, the pilot pressure output from the solenoid proportional valve is proportional to an operation signal output from the operating device up to an upper limit pressure, and When the swing unit is an arm, the center of gravity of the arm and the bucket as a whole, and when the swing unit is a bucket, the center of gravity of the bucket is at least the vertical line passing through the swing center of the swing unit. A hydraulic excavator drive system that controls the solenoid proportional valve so that the upper limit pressure increases as the swinging portion is farther from the cabin as long as it is located on the same side as.   When the operating device receives the second operation, the control device sets the upper limit pressure to increase as the swinging part is farther from the cabin, in the entire swinging range of the swinging part. The hydraulic excavator drive system according to claim 5, wherein the solenoid proportional valve is controlled. Revolving structure,
And a camera attached to the revolving structure for photographing the swinging unit,
The control device obtains a swing angle between the vertical line and the line connecting the center of gravity and the swing center of the swing portion from the image captured by the camera, and determines the swing angle according to the swing angle. The hydraulic excavator drive system according to claim 1, wherein the upper limit pressure is determined. A traveling body that supports the revolving structure so that the revolving structure is revolvable,
An inclination sensor attached to the revolving structure for detecting the levelness of the revolving structure,
The vertical line is a virtual straight line parallel to the turning axis of the turning body,
The hydraulic excavator drive system according to claim 7, wherein the control device corrects the swing angle obtained from an image captured by the camera based on the horizontality detected by the tilt sensor.

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